Biomedical subjects

Antônio C Roque

Publications and source records attributed to Antônio C Roque.

4 recordsLinked to original sources

PubMed2004

A biophysical model of vertebrate olfactory epithelium and bulb exhibiting gap junction dependent odor-evoked spatiotemporal patterns of activity.

This work describes a biophysical model of the initial stages of vertebrate olfactory system containing structures representing the olfactory epithelium and bulb. Its main novelty is the introduction of gap junctions connecting neurons both in the epithelium and bulb, and of biologically detailed dendrodendritic synapses between granule and mitral cells in the bulb. The model was used to simulate the effect of an odor presentation on the neural activity pattern in the epithelium and bulb. During the time for which an odor is presented with a constant concentration, there are spatiotemporal patterns in the epithelium and bulb generated by the couplings due to the gap junctions and/or dendrodendritic synapses. A study varying the strength of the gap junction coupling shows that the spatiotemporal patterns, both in the epithelium and bulb, are dependent of the coupling strength. It is also shown that the olfactory bulb's spatiotemporal pattern depends on the existence of the dendrodendritic connections between mitral and granule cells. If these spatiotemporal patterns really exist in the early processing stages of the olfactory system they may be used for odor coding and the gap junctions and dendrodendritic synapses might have a role on it.

Animals↗

PubMed2002

Physics of psychophysics: Stevens and Weber-Fechner laws are transfer functions of excitable media.

Sensory arrays made of coupled excitable elements can improve both their input sensitivity and dynamic range due to collective nonlinear wave properties. This mechanism is studied in a neural network of electrically coupled (e.g., via gap junctions) elements subject to a Poisson signal process. The network response interpolates between a Weber-Fechner logarithmic law, and a Stevens power law depending on the relative refractory period of the cell. Therefore, these nonlinear transformations of the input level could be performed in the sensory periphery simply due to a basic property: the transfer function of excitable media.

Journal Article↗

PubMed2002

Mammography and computerized decision systems: a review.

Computer-aided diagnosis (CAD) systems in mammography have been developed and investigated for several years and recently they have left the research stage to enter the clinical stage. The purpose of this article is to review the present situation of mammography for breast cancer detection and the role played by CAD systems. Results from the recent literature show that CAD systems have the potential to improve the sensitivities of radiologists in the detection of malignant clustered microcalcifications and masses, while keeping specificities at acceptable levels. This leads to the conclusion that CAD systems can be incorporated into clinical practice as a double reading option to radiologists. However, some issues have yet to be tackled for CAD systems to gain better acceptance and more widespread use worldwide.

Breast Neoplasms↗

PubMedDate not supplied

A dynamical model of fast cortical reorganization.

In this work we study the connection between some dynamic effects at the synaptic level and fast reorganization of cortical sensory maps. By using a biologically plausible computational model of the primary somatosensory system we obtained simulation results that can be used to relate the dynamics of the interactions of excitatory and inhibitory neurons to the process of somatotopic map reorganization immediately after peripheral lesion. The model consists of three regions integrated into a single structure: tactile receptors representing the glabrous surface of the hand, ventral posterior lateral nucleus of the thalamus and area 3b of the primary somatosensory cortex, reproducing the main aspects of the connectivity of these regions. By applying informational measures to the simulation results of the dynamic behavior of AMPA, NMDA and GABA synaptic conductances we draw some conjectures about how the several neuronal synaptic elements are related to the initial stage of the digit-induced reorganization of the hand map in the somatosensory cortex.

Animals↗